Broken manifold stud in head
were you using a craftsman extractor? they are junk, too brittle and break way to easy
I use to break them off all the time and then Dad would use a punch and get it out then use his extractors from work and back thew broken bolt/stud out every time
Now that dad is gone I have to be more carefull not to break them off ............LOL but I do have his extractors now
I would also recommend taking it to a machine shop, save the time and aggervation and not damage the head beyond repair.